using UnityEngine;
using System;
using AX.AudioSystem;

/// <summary>
/// 录音机，表示一个音频录制器。
/// </summary>
[RequireComponent(typeof(AudioSource), typeof(PromptTone))]
public class AudioRecorder : MonoBehaviour
{
    [Header("音频录制设备的 Id")]
    public int DeviceId = 0;
    [Header("音频采样率")]
    public int SamplingRate = 8000;
    [Header("音频录制最大时长，按秒计")]
    public int RecordMaxTime = 60;

    public event Action Started;
    public event Action<ArraySegment<byte>> Stopped;

    private volatile bool isRecording;

    private TimeSpan timeSpan;
    private DateTime startTime;

    private AudioSource audioSource;
    private OpusEncoder opusEncoder;
    private BetterList<byte> opusBuffer;
    private float[] audioBuffer;
    private float[] packageBuffer;
    private byte[] frameBuffer;
    private int packageSize;

    /// <summary>
    /// 表示音频录制器是否已经准备就绪。返回 true 表示准备就绪；返回 false 表示当前没有录制设备。
    /// </summary>
    public bool Ready
    {
        get { return Microphone.devices.Length > 0; }
    }

    /// <summary>
    /// 表示音频录制器当前是否正在录制中。
    /// </summary>
    public bool IsRecording { get { return isRecording; } }

    /// <summary>
    /// 表示单声道录制还是双声道录制。
    /// </summary>
    public int Channels
    {
        get { return audioSource.clip.channels; }
    }

    void Start()
    {
        audioSource = GetComponent<AudioSource>();

        timeSpan = TimeSpan.FromSeconds(RecordMaxTime);
        frameBuffer = new byte[OpusEncoder.PacketMaxSize];
    }

    void Update()
    {
        if (IsRecording && DateTime.Now - startTime >= timeSpan)
            StopRecorder();
    }

    void OnDestroy()
    {
        if (opusEncoder != null)
        {
            opusEncoder.Dispose();
            opusEncoder = null;
        }
    }

    public void StartRecorder()
    {
        var clip = Microphone.Start(Microphone.devices[DeviceId], false, RecordMaxTime, SamplingRate);

        if (opusBuffer == null)
        {
            opusEncoder = new OpusEncoder((SamplingRate)SamplingRate, (Channel)clip.channels);

            packageSize = opusEncoder.FrameSize * 1;
            opusBuffer = new BetterList<byte>(200 * 1024);      // 200KB 大概相当于录音 60 秒编码的长度
            packageBuffer = new float[packageSize];
        }

        var length = clip.samples + PromptTone.Data.Length;
        if (audioBuffer == null || audioBuffer.Length < length)
            audioBuffer = new float[length];

        audioSource.clip = clip;
        audioSource.mute = true;
        audioSource.Play();

        startTime = DateTime.Now;
        isRecording = true;

        OnStarted();
    }

    public bool StopRecorder()
    {
        if (!isRecording)
            return false;

        var device = Microphone.devices[DeviceId];
        var pos = Microphone.GetPosition(device);

        // Unity3D 的 Microphone 获取的位置有时候会超过上限
        // 因此限定一下，以免数组越界
        pos = Math.Min(pos, audioSource.clip.samples);

        Microphone.End(device);
        audioSource.Stop();

        if (pos > 0)
            audioSource.clip.GetData(audioBuffer, 0);

        Array.Copy(PromptTone.Data, 0, audioBuffer, pos, PromptTone.Data.Length);

        var length = pos + PromptTone.Data.Length;

        for (var i = 0; i + packageSize <= length; i += packageSize)
        {
            Array.Copy(audioBuffer, i, packageBuffer, 0, packageBuffer.Length);

            var encoded = opusEncoder.Encode(packageBuffer, frameBuffer);

            opusBuffer.Add((byte)encoded);
            opusBuffer.AddRange(frameBuffer, 0, encoded);
        }

        Destroy(audioSource.clip);
        audioSource.clip = null;

        isRecording = false;

        OnStopped(new ArraySegment<byte>(opusBuffer.GetBuffer(), 0, opusBuffer.Count));

        opusBuffer.Clear();

        return true;
    }

    protected virtual void OnStarted()
    {
        if (Started != null)
            Started();
    }

    protected virtual void OnStopped(ArraySegment<byte> data)
    {
        if (Stopped != null)
            Stopped(data);
    }
}